The exterior surfaces of houses and other structures are often protected by exterior siding products made from wood, vinyl, aluminum, bricks, stucco, fiber-cement and other materials. Wood and fiber-cement siding (FCS) products, for example, are generally planks, panels or shakes that are "hung" on plywood or composite walls. Although wood siding products are popular, wood siding can become unsightly or even defective because it may rot, warp or crack. Wood siding products are also highly flammable and subject to insect damage. Therefore, wood siding products have several drawbacks.
FCS products offer several advantages compared to other types of siding materials. FCS is generally a composite material composed of cement, silica sand, cellulose and binders. To form FCS panels and planks, a liquid fibercement composite is rolled or pressed into the shape of the planks or panels, and then the fiber-cement composite is cured. FCS is advantageous because it is nonflammable, weatherproof, and relatively inexpensive to manufacture. moreover, FCS does not rot and insects do not consume the fiber-cement composites.
FCS products are typically installed by a siding contractor at a particular job site or a modular home manufacturer in a factory. To install FCS planks, for example, the planks are cut to a desired length and then nailed to plywood or wood-composite panels in a manner similar to hanging planks of cedar siding. After the FCS is installed, trim materials are generally attached to the structure. The FCS and the trim materials are subsequently painted.
FCS is often cut using an abrasive disk in a manner similar to cutting wood products with a hand-held power saw or a table saw. Cutting FCS with an abrasive disk, however, generates a very fine dust that creates an unpleasant working environment. The fiber-cement composite materials are also highly abrasive, and thus the abrasive-disks may wear out quickly. Thus, there are many disadvantages to cutting FCS with an abrasive disk.
FCS may also be cut with shears having opposing blades or hand-held cutting tools having a reciprocating cutting blade. Pacific International Tool & Shear, Ltd. has developed several shears and hand-held cutting tools, including those set forth in U.S. Pat. Nos. 5,570,678 and 5,722,386 (the "Pacific Patents"), and U.S. patent application Ser. No. 09/036,249, all of which are herein incorporated by reference. Several embodiments of the shears disclosed in the Pacific Patents have an actuator, an upper blade assembly coupled to the actuator to move along a cuffing path, and a lower blade assembly positioned under the upper blade assembly. The upper blade assembly has an upper blade, and the lower blade assembly has a lower blade. The shears disclosed in the Pacific Patents can also have first and second support members on either side of the lower blade, and the first and second support members can have first and second support surfaces in a common workpiece support plane. The lower blade in the Pacific Patents is configured such that its cutting edge is either at the support plane or projects slightly above the support plane toward the upper blade. In operation, a workpiece slides across the lower blade until a desired cutting plane is aligned with the upper and lower blades. The actuator then drives the upper blade against an upper surface of the FCS workpiece to penetrate the upper and lower blades into opposite sides of the workpiece. The upper and lower blades generate a crack that propagates along the cutting plane through the workpiece to cut the workpiece along the cutting plane.
Although the shears disclosed in Pacific Patents cut a clean edge in FCS without producing dust, one operating concern of these shears is that it can be difficult to cut long sections of an FCS workpiece in a single stroke of the blades. For example, to cross-cut a 4'.times.8' panel of 1/4-inch thick FCS, Pacific International Tool and Shear developed a shear similar to those described in U.S. Pat. No. 5,570,678 that required three pneumatic cylinders operating at a pressure of 150 psi. The same shear, however could not cross-cut a 4'.times.8' panel of 5/16-inch thick FCS operating at a pressure of 150 psi in each pneumatic cylinder. One solution to this problem is to use more force to drive the upper and lower blades into the FCS workpiece, but this solution requires larger and/or more actuators that significantly increases the cost and the number of moving components that can malfunction.
Another operating concern of the cutting tools disclosed in the Pacific Patents is that the upper and lower blades may wear relatively quickly. FCS quickly grinds or otherwise abrades most metals because it is highly abrasive. As a result, any contact with FCS dulls the cutting edges of the upper and lower cutting blades. The lower blades of the shears disclosed in the Pacific Patents are particularly susceptible to wear because the FCS workpiece typically slides across the edge of the lower blade to position a cutting line on the workpiece between the upper and lower blades. Thus, even though the shears disclosed in the Pacific Patents work well in many applications, there is a need to efficiently cut long sections of FCS and reduce wear of the cutting blades.